This invention relates to magnetic streamlining and flow control in tundishes.
Continuous casting is a major advance in the processing of metallic melts. In this operation the molten metal, which may be steel, aluminum, copper or the alloy of several metals, is poured from a ladle (or more infrequently directly from a furnace) through an intermediate vessel, called a tundish, into molds, where solidification takes place, yielding continuous slabs, billets or bars.
In most conventional steel (including stainless steel) applications this tundish is a trough, some several meters long, about a meter deep and a meter wide. Molten metal is poured into the tundish at one point and molten metal streams are discharged through two or more outlet nozzles. Initially the main role assigned to these tundishes was to distribute the liquid and to act as a buffer ensuring uniform metal flow. More recently it has been appreciated that the operation of tundishes play a key role in affecting the quality of continuously cast steel products.
This is due to several factors. One of these is that for properly designed tundishes flow disturbances, such as vortexing and flow fluctuations are minimized, which then result in the products having a better surface quality. Another is that for properly designed tundishes non-metallic impurities, termed inclusions, will have an opportunity to float out, resulting in a product of superior quality. Yet in other applications proper tundish design can minimize the temperature fluctuations in the system and allow for a uniform temperature of all the exiting streams. Furthermore, better control of the temperature in tundishes may be achieved through auxiliary heating.
The recognition of these factors had led to extensive physical (water) and mathematical modeling of tundish systems, in order to improve the quality of continuously cast products. Several known, well documented tundish designs include the use of dams, weirs and other internal elements, having the objective of providing flow control. Yet these efforts have not been fully successfuly, because significant dead zones may exist in the lee of the dams and the weirs, reducing the effective tundish volume.
In addition to tundishes used in the conventional continuous casting of steel, which are troughs of the type described above, other types of tundishes also exist, notably in the processing of non-ferrous metals and in association with novel continuous casting proceses.
In many of these operations the tundish is a shallow pan, having a depth of say 50-250 millimeters, with the other dimensions ranging from a few hundred to a few thousand millimeters. Typically these systems have one inlet and one or two outlets. The main function of these tundishes is to provide for an even distribution of the flow from the ladle to the mold. In many of these applications, particularly those involving the new continuous casting systems, such as single or double roll continuous casting operations, belt casters and the like, the ability to provide a smooth, spatially uniform flow is a critical requirement.